In the vehicle lower portion structure disclosed in Japanese Patent Application Laid-Open (JP-A) No. S58-153175, a floor cover (undercover) covers substantially the entire surface of a vehicle floor from the vehicle lower side. Due thereto, the lower portion of the vehicle can be structured by a flat surface by the floor cover. As a result, the air resistance of the vehicle can be lessened, and the aerodynamic performance of the vehicle can be improved.